Don't use composer manager module, this is no more needed as of Drupal 8.1

Uninstall a module:

Always uninstall a module in this 2 step way:

drush pm-uninstall {module_name}

composer remove drupal/{module_name}

Other:

You can always see latest library and module versions installed in composer.lock file.

Deploying modules to other devs or production:

Now you added a module locally through composer and want to push it? Since modules are now ignored in git, only thing that will be pushed is depenency in composer.json. Therefore to deploy the module, each developer will need to rebuild its dependencies using

"composer install".

Drupal configuration manager will take care if the module is enabled or not. However order must be respected so you should import new configuration only after composer install is run, otherwise you might get a error.